`timescale 1ns/10ps
module inv (
    A,Y
);
    input A;
    output Y;
    assign Y=~A;
endmodule

module inv_tb;
reg aa;
wire yy;
inv inv(.A(aa),.Y(yy));

initial begin
    aa<=0;
    #10 aa<=1;
    #10 aa<=0;
    #10 aa<=1;
    #10 aa<=0;
    #10 aa<=1;
    #10 $stop;

end
    
endmodule